What road wheels and tires and gravel wheels and tires?
This stuff seems so difficult to measure. While the average power is pretty good, what did the graph look like during the interval? On gravel was it difficult to take the same line every time? Was there wind? Did the temperature change that could impact the power meter slightly? Once the tires get warmed up, how does that impact results?
The questions could go on and on⌠which is what makes this so difficult. And what makes those willing to experiment so valuable. I think many just throw numbers out without any form of validation. So I guess this is a long way to say thanks for all the effort and trying to put some kind of data to the hypothesis. Itâs not easy!
OK so donât laugh. Gravel setup is the e thirteen piedmont wheels with a 2.1" thunder burt super ground addix speed rear and 45mm vittoria strada bianchi (the handmade one) in front. I rode this setup in big sugar. Inserts on both ends. On the road setup itâs the bontrager Aeolus pro 3v wheels with a 32mm conti 5000 in back and a pirelli p zero up front, both tubeless with an insert in the rear. So a mishmash but, in general, your typical fast-ish road setup and fast gravel setup.
Joe
1 Like
âChallenging at best, deeply problematic at worstâ LOL, I hear you!
This was on new smooth pavement so we didnât have the âline in gravelâ issues but there was some wind and the temp probably varied a little (test took about an hour so maybe not too bad on temp). I havenât seen tires get faster when they warm up but itâs something to watch for (hadnât considered it).
As far as where is the power delivered during the lap, that seems to make surprisingly little difference. And I like time trials so the concept of âpush a little on the hills and back off a little on the descents for a faster time than a steady powerâ is taken as truth. But I havenât been able to prove it matters muchâŚif at all. I think if you run a lap a whole bunch of times going for consistency youâll end up putting down the power similarly run-to-run. I try to keep it steady and keep an eye on ave power as the lap progresses but Iâm sure there is plenty of variability there. Iâm just not convinced either way about it mattering (maybe it doesâŚmaybe not?)
1 Like
OMG triggering! You run a lot of laps and look at the data and itâs likeâŚâif we take lap 4 and 9 then these setups are the same but if we look at laps 2 and 7 then A is way faster than Bâ so when you see a youtube video with one trial for each setupâŚeven if they are using power to measure the effortâŚitâs likeâŚwow that told us nothing.
Joe
2 Likes
Itâs good that youâre aware of that. Iâm sure a lot of people that do testing, targeting a fixed average power per run, donât realise that by pushing a bit harder in the ârightâ places, on the uphills, in an effort to bring the average back up towards the target power, it affects their overall times/average speeds, even though their average powers are spot on their target.
Thereâs a lot of potential pitfalls with testing, but the fairly small variations seen in your lap-to-lap times, and also the stint-to-stint time variation, provide some really good insights into the precision of the test method.
Regarding temperature, I remember than Tom Anhalt derived a relationship between temperature and CRR (see plot in this blog post), albeit it with a fairly limited number of test points. It would be good to know if thereâs any other data out there. Intuitively, it seem right that a warmer tyre would be more supple and have less hysteresis losses (like a squash ball, once it becomes warm).
2 Likes
Just fitted the new Schwalbe G-One RS 50mm on my Checkpoint SLR 9 (2023 model). Looks like itâs going to be a great tire and fit. Excited to give it a go coming from the older version 45mm.
9 Likes
Nice, is this tire in the BRR queue for testing?
BRR has performed a CRR at temperature test as well: CRR Temperature Test | Bicycle Rolling Resistance
2 Likes
I see that you weighed at least one of them. Did you weigh both? I just got a set and they are 587 and 604 grams. Spec says 585 so Iâm wondering how we have such a variance between us. I know weâre not supposed to care about weight anymore, but Iâm also worried about quality control at Schwalbe.
2 Likes
I weighed both of them. I think the other one was 564.
Iâve had the same experience with Maxxis, Vittoria and Perelli. The weights will always vary and I wouldnât worry about it, but I understand the feeling.
3 Likes
Interesting finding while checking RC 2.2 fit on my bike. There is quite a bit of difference with similar internal width rims. I have tried the tires with 3 different rims (IR 23 mm, 24mm and 24.5 mm ) and one of them provides 4-5 mm more clearance than the other two
Whatâs the internal width of the rims theyâre mounted on? Iâm running a 48mm tufo thundero on my checkpoint in the back, and itâs pretty tight.
I forgot that BRR did a test too, thanks. It looks like BRR measured approximately 1% change in CRR per 1 degree C change in temperature, which is a bit less than Tom Anhaltâs 1.36% per degree C sensitivity. Itâs broadly similar though, and it might be affected by drum/roller diameter, I guess.
Curious that you have the more aggressive tyre on the back and the less aggressive on the road - Usually this would be the other way round. I run TB 2.1 front and 50mm near slick on the rear.
Front wheel bite in the corners is v nice, back just follows.
Exactly. Iâve already had a few instances of tests that seemed identical, looking at average speed and powerâŚ
But once it is actually in Aerolab you can start to pull apart the differences.
Dylan Johnson has a rebuttal of sorts to the Nathan Haas podcast bit above. Starts at 56:20 and gets a little convoluted but raises some of the same points as here with some more info on testing heâs done and others as well.
2 Likes
I was looking at gravel/XC tires in the 2.0"-2.1" range, that have yet to be tested on BRR (i.e. large tires for those that canât quite fit Race Kings). There are a lot out there but very few that have the potential to be fast. So far, the only ones I could find are
- Schwalbe G-One RS/RX Pro 50 (RS is next in line on BRR, RX is the knobbier version)
From the post above, these come in below 50mm, which is probably too narrow.
- Vittoria Terreno XC Race 2.1 (Lachlan ran one of these in the front at Unbound)
According to Vittoria, the Terreno XC is their fastest XC tire, the ranking goes Terreno>Peyote>Mezcal>Barzo. I would like to see how this one performs. I found an old review that said they measured up to 54mm which would be pushing it clearance wise for me.
Iâm currently running 2.1 Thunder Burts. Any other tires to be aware of?